We use space and time-resolved dynamic light scattering in the highly multiple scattering regime (Diffusing Wave Spectroscopy, DWS) to probe the microscopic dynamics of amorphous solids during mechanical tests. Our experiment allows us to measure a coarse-grained map of the microscopic motion in the sample, by measuring the local mean squared displacement down to a resolution of a fraction of nm², averaged over regions of interest (ROIs) of typical size of tens of microns. Additionally, we measure the mesoscopic drift of the same ROIs defined for the microscopic dynamics.
We study a semi-crystalline polymer (PolyEther Ether Ketone, PEEK) and an elastomer (PolyDiMethylSiloxane, PDMS) charged with particles (Titanium dioxide, TiO2) sized of 300nm, submitted to elongational mechanical tests.
The test protocol consists of several stretching steps, each of them followed by a relaxation step during which the elongational strain is kept constant. The test is run until the material macroscopically fractures.
These experiments show the interest of this technique as a method to predict and localize an eventual failure of a material.
|Category||Short file description||File description||File Size|